Overwhelmed single parents with unruly kids are rescued by a magical nanny who seemingly appears out of nowhere. And at no cost! For some older moviegoers escorting little ones, this premise might be impossibly alluring. And they said fans of “Avatar” were depressed when they left the theater.

“Nanny McPhee Returns” is the sequel to 2005’s “Nanny McPhee.” Both were written by Emma Thompson (who stars as the nanny in question) based on Christianna Brand’s Nurse Matilda books, which were published in the 1960s and ‘70s.

That McPhee owes much to P.L. Travers’ Mary Poppins is obvious, and there’s a whiff of familiarity to both Nanny McPhee movies that prevent them from being truly fresh. But there’s still a warm, British naturalism to “Nanny McPhee Returns” and an old-fashioned cheerfulness uncommon to most of today’s kids movies.

In the first installment, McPhee, a mean-looking witch clad in black, came to the aid of a widowed father (Colin Firth). This time around, she arrives to help Isabel Green (Maggie Gyllenhaal, with British accent in tow), a mother of three and wife to a farmer off fighting in World War II.

The particular war is never mentioned, but WWII is the film’s clear setting. A young nephew, Cyril Gray (Eros Vlahos) and his sister Celia (Rosie Taylor-Ritson) have been sent from their wealthy home in London to their aunt’s thatched-roofed farm house, an appalling development to their refined tastes. Eyeing the muddy farm, Cyril promptly declares it the “land of poo.”

They immediately clash with Isabel’s three children: Norman (Asa Butterfield), Megsie (Lil Woods) and Vincent (Oscar Steer). Isabel is drowning in the chaos, made worse by her ditzy candy shopkeeper (Maggie Smith).

McPhee arrives mysteriously, introducing herself (“little ‘c,’ big ‘P”’) as an “army nanny” who has been “deployed.” The government pays her way, she informs Isabel, though one can bet that free, magical nannies would surely be among those to fall victim in Britain’s current, deep budget cuts.

Thompson’s McPhee is a fairly wonderful creation. With two large moles, an overgrown front tooth, a monobrow and a protruding, bulbous nose, she appears a mean crone. But it’s all merely a facade to a deeply caring shepherd of misbehaving children: She’s the fairy godmother of tough love. As the children learn each of her five lessons, McPhee’s deformities disappear.

The main source of drama (for McPhee wins the kids over quickly) comes from Isabel’s brother-in-law, Phil (Rhys Ifans). Dressed in a shabby blue pinstripe suit, he looks like an outcast from “Guys and Dolls.” He has gambled the farm away, even though it’s only half his.

It’s worth noting that even in a cartoonish kids movie like this, what a great presence Ifans has. Since becoming known to most in 1999’s “Notting Hill,” he has steadily — and perhaps surprisingly, considering the jokiness of that early part — shown that he can enliven most any film and fill most any character. He has had a good 2010, too, appearing in the latest “Harry Potter,” archly narrating the Banksy film “Exit Through the Gift Shop” and, especially, playing Ben Stiller’s best friend in “Greenberg.”

Capably directed by Susanna White (making her feature film debut after some notable TV work) “Nanny McPhee Returns” is slightly less scatterbrained than the original, but keeps its Day-Glo Victorian palette full of color and whimsy.

The predictable story turns (the father away at war is handled as you’d expect, with worry followed by a miraculous homecoming) and the infrequently funny dialogue keep the film from quite taking off. But one can quibble only so much with a family friendly film that so brightly preaches those not-exactly-hip tenets of country living and manners.

When McPhee and two of the children make a trip to London (awash in zeppelins and double-decker buses), they meet a former pupil of McPhee’s, now a Royal guard soldier. It’s clear that the country itself has been made from McPhee’s mettle. Cut government services warily, Britain.

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